Composition of porous element for biomaterial

ABSTRACT

A composition of a porous body for use as biomaterial according to the present invention is produced by adding Al (aluminum) in the amount of 0.1 to 3.0 atomic % to a porous composition consisting of titanium, nickel, iron and molybdenum, and it promotes the growth of living tissue and cells into pores. By the addition of Al to Ni, Ti, Fe and Mo, the temperature of formation of the liquid phase is lowered, and thus the diffusion of the constitutional elements of the composition is promoted, and the uniform distribution of the constitutional elements increases. As a result, the proportion of micropores in the porous body becomes increased to the extent that the distribution of micropores having the size in the range of 10 −2  μm˜10 μm is more than 5% in the metal bridge.

FIELD OF THE INVENTION

The present invention relates to an alloy composition of TiNi porousbody for utilizing as biomaterial, and more particularly to an alloycomposition comprising a Ti—Ni—Fe—Mo alloy material and aluminum (Al),which causes an increased number of micropores in a porous body and thuscauses the growth of cells and living tissue to be activated asbiomaterial.

BACKGROUND OF THE INVENTION

Generally, a porous alloy primarily comprising Ti—Ni, with Fe and Moadded thereto, has been manufactured by the method of self-propagatinghigh temperature synthesis (hereinafter referred to as “SHS”) and hasbeen extensively used as biomaterial in the medical field due to itspore structure, good mechanical properties, high biocompatibility, andfunctional properties such as shape memory effect and pseudoelasticity.

For example, in the field of surgery, in order to prevent the secondaryinfection on an open infected area and to provide an advantageouscondition for regeneration of living tissues, the porous body was usedby impregnating the pores therein with antibiotics, and satisfactoryresults have been obtained. Further, the porous TiNi based alloy hasbeen used in the field of tissue engineering, wherein living cells arecultivated in vitro and transplanted to a living body to replace livingtissue. Furthermore, in the field of orthopedics surgery, the porousTiNi based alloy has been used as a scaffold which plays a role of anincubator for cultivating living tissue and cells and is transplanted toa living body as an artificial bone or a bone replacement. It is theporous structure that allows the transport of body fluid and providesadvantages for the in-growth of new bone tissue into the pore, makingthe fixation of implant more natural and reliable.

The characteristics of pores in the porous body such as porosity, meanpore size, and the distribution of pore sizes are very important indetermining whether the porous body can be applied to various medicalfields as biomaterial, since physical and mechanical properties of theporous body such as shape memory, pseudoelasticity, fatigue resistance,and mechanical stability depend on the characteristics of pores. If theporous TiNi based alloy having small pores or micropores of a size inthe range of 10⁻² μm˜10 μm in a metal bridge is used as a scaffold, theadaptability of the porous body as biomaterial can be highly enhanced.

Controlling pore sizes and their distribution, which constitute thecharacteristics of pores of the porous body, depends on the compositionratios of the components of the porous alloy composition and theprocedural variables of the self-propagating high temperature syntheticmethod.

In a composition of a conventional porous body for medical purposes,which comprises titanium, nickel, iron and molybdenum, problems wereencountered in that the distribution of micropores of the porous bodyhaving the size in the range of 10⁻² μm˜10 μm is less than 5% in themetal bridge.

However, in order to provide an alloy composition used as an effectiveand useful biomaterial wherein the growth of tissue and cells into poresis increased and the characteristics of the porous body as biomaterialare improved, the distribution of micropores should be more than 5%.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a composition of aporous body for use as biomaterial which substantially obviates theproblems caused by limitations and disadvantages of the prior art. Thatis, according to the present invention, a composition of a porous bodyfor use as biomaterial, which is produced by adding Al (aluminum) to aporous composition consisting of titanium, nickel, iron and molybdenum,and by which the distribution of micropores is increased, so that thegrowth of living tissue and cells into pores can be increased, isprovided.

These and other advantages and purposes of the present invention areachieved by a composition of a porous body which consists of nickel,titanium, iron and molybdenum and further comprises aluminum to promotethe distribution of micropores.

By the addition of aluminum to the components of nickel, titanium, ironand molybdenum, composition ratios of the components are changed, andthus, the distribution of micropores becomes considerably increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a microscopic photograph showing the structure of pores formedon the surface of a porous body composition for use as biomaterial,which consists of titanium and nickel; and

FIG. 2 is a microscopic photograph showing the structure of pores formedon the surface of the porous body composition for use as biomaterial,which comprises titanium, nickel, iron, molybdenum and aluminumaccording to a preferred embodiment of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to preferred embodiments of thepresent invention, an example of which is illustrated in FIG. 2.

Composition ratios of a preferred embodiment are summarized in thefollowing Table 1. It is apparent to those skilled in the art that thecomponent ratios as shown in Table 1 are not to limit the presentinvention but simply illustrate a preferred embodiment of the presentinvention.

TABLE 1 Composition ratios of the composition according to a preferredembodiment Components Ratio (atomic %) Nickel (Ni) 48.0˜52.0 Iron (Fe)0.02˜3.0  Molybdenum (Mo) 0.1˜2.0 Aluminum (Al) 0.1˜3.0 Titanium (Ti) 40.0˜51.78

The most characteristic feature of the present invention resides in thechange of composition ratios caused by the addition of aluminum totitanium, nickel, iron and molybdenum. Preferred composition ratios are48.0˜52.0 atomic % of nickel, 0.02˜3.0 atomic % of iron, 0.1˜2.0 atomic% of molybdenum, 0.1˜0.3 atomic % of aluminum and 40.0˜51.78 atomic % oftitanium, as listed in the above Table 1.

The reasons for the addition of aluminum and the results thereof areexperimentally proved, and they can be explained by referring to the SHSprocess.

The SHS process is simple and highly advantageous in terms of energy.That is, in the SHS process, powders of components constituting acomposition are mixed according to relevant composition ratios andformed in a certain shape, and then the shaped body is ignited at oneend thereof. By the ignition of the shaped body in high temperatures,combustion occurs on the surface of the shaped body, and it propagatesby itself through the surface of the body, to form a porous body.

In the SHS process, micropores in the porous body are formed during thecourse of rearrangement of the liquid phase formed by the combustion inhigh temperatures and the gases generated by the evaporation ofimpurities on the surface of the shaped body.

The combustion of the raw material powders occurs on the surface of theshaped body, and the propagation of the reaction is controlled by thediffusion of the components of the composition. By the addition of acomponent of the alloy, i.e., aluminum in the present invention, themelting point of the composition at which the liquid phase is formedchanges, and such a change greatly influences on the area where theliquid phase exists and the rearrangement of the liquid phase.

Specifically, when Al is added to Ni, Ti, Fe and Mo, the melting point,i.e., the temperature of formation of the liquid phase is lowered, andthus the range of temperatures in which the liquid phase can be formedby combustion becomes wide.

In addition, as the range of temperatures where the liquid phase isformed is expanded, the diffusion of the constitutional elements of thecomposition in the liquid phase is promoted, and the uniformdistribution of the constitutional elements increases, and as a resultthe proportion of micropores in the porous body becomes increased to theextent that the distribution of micropores having the size in the rangeof 10⁻² μm˜10 μm is more than 5% in the metal bridge.

Furthermore, the composition ratios of the constitutional elements arechanged by the addition of Al to Ni, Ti, Fe and Mo, and thus thetemperature of initial ignition in the SHS process becomes lower thanthe temperature required for the combustion of the compositionconsisting of Ni, Ti, Fe and Mo. This indirectly proves that thetemperature range where the liquid phase is formed becomes expanded.

Preferably, the composition ratio of aluminum in the compositionaccording to the present invention is 0.1 to 3.0 atomic %.

If the composition ratio of aluminum is less than 0.1 atomic %, theaddition of Al does not increase the distribution ratio of micropores inthe porous body, and even the distribution of micropores becomesdecreased.

If the composition ratio of aluminum is more than 3.0 atomic %, theliquid phase is excessively formed, and micropores are not sufficientlyformed, so that the porosity of the porous body deteriorates.

Therefore, it is not preferred that Al is added in the ratio of lessthan 0.1 atomic % or more than 3.0 atomic %.

Meanwhile, in the porous body composition according to the presentinvention, titanium and nickel are used since the mixed powders oftitanium and nickel causes the composition to have pseudoelasticitywhich is substantially similar to the elasticity of bones of the humanbody. Also, they cause the composition of the present invention to havean excellent biocompatibility to the bone structure of the human body,so that the composition can be used as biomaterial such as in implantsfor teeth.

Further, the use of molybdenum (Mo) improves the stability of the phasein the synthetic process with titanium and nickel powders.

The composition of a porous body for use as biomaterial according to thepresent invention was prepared by the SHS process to form a certainproportion of micropores of the size in the range of 10⁻² μm to 10 μm.

Specifically, Ni, Ti, Fe, Mo and Al powders were prepared according tothe composition ratios as shown in Table 1, that is, Ni 48.0˜52.0 atomic%, Fe 0.02˜3.0 atomic %, Mo 0.1˜2.0 atomic %, Al 0.1˜3.0 atomic % and Ti40.0˜51.78 atomic % by measuring weights of the respective raw materialpowders. Each of the raw materials was weighed within the accuracy of±0.1 mg, and the weight of the entire composition was within theaccuracy of ±10 mg.

The raw material powders were mixed in a powder mixing machine under theenvironment of inert argon gas for 6 to 8 hours according to a drymixing process.

The powder mixture was dried in a vacuum chamber under a temperature of350 to 360K for about 7 hours. The holding of the powder mixture at thistemperature for about 6-8 hours is sufficient for removal of themoisture and for reliable ignition and further combustion of themixture. Then, the powder mixture was consolidated by tapping method.

The consolidated powder mixture was placed in a cylinder reactor made ofstainless steel, and the reactor was ventilated with inert gas (Ar gas).Argon gas was supplied in a constant pressure, and the powder mixturewas heated in a furnace by applying power to an ignitor.

Then, when the heating process was completed, the reactor was evacuatedfrom the furnace and then it was cooled with water and during thisprocedure the inert Ar gas was continuously supplied.

The porous body manufactured by the above procedures had the porousstructure in which micropores of 10⁻² μm˜10 μm are formed in theproportion of more than 5%. It is compared with the conventional porousbody manufactured by the alloy of Ni, Ti, Fe and Mo only as shown inFIG. 1.

INDUSTRIAL APPLICABILITY

The alloy composition according to the present invention, which ischaracterized in that aluminum is added to the porous Ti—Ni—Fe—Mo alloymaterial, has an increased proportion of micropores of 10⁻² μm to 10 μmmore than 5% and thus activates the growth of cells and living tissue inthe porous body. Therefore, the alloy composition according to thepresent invention can be used as biomaterial, and it can be applied tovarious medical fields.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thepresent invention covers the modifications and variations thereofprovided they come within the scope of the appended claims and theirequivalents.

1. A composition, of a porous body for use as biomaterial comprising Ni,Ti, Fe, Mo, and Al to increase the distribution of micropores in theporous body, wherein composition ratios of Ni, Ti, Fe, Mo and Al in thecomposition are respectively Ni 48.0 to 52.0 atomic %, Ti 40.0 to 51.78atomic %, Fe 0.02 to 3.0 atomic %, Mo 0.1 to 2.0 atomic % and Al 0.1 to3.0 atomic %.